The invention relates to a radiation detector for detection of X-ray radiation, which is constructed with a GaN-based semiconductor material. Furthermore, the invention concerns a measuring device, which contains at least one such radiation detector, and applications of the radiation detector and of the measuring device.
It is known to use Gallium nitride (GaN) in semiconductor detectors for detection of X-ray radiation. For example, a GaN sensor is described in US 2010/0069749 A1, which emits luminescent light in response to a X-ray radiation. The luminescent light is conducted from the sensor via a light guide to a photodetector. This technique has disadvantages, since the combination of the sensor with the light guide represents a sensitive structure and since the detected X-ray radiation is not directly converted in an electric measurement signal.
Furthermore, in “Applied Physics Letters” Vol. 92, 2008, pp. 263501, J.-Y. Duboz et al. analyze the suitability of GaN for detection of X-ray radiation. For this purpose, GaN layers, e.g. with a thickness of 110 μm or 480 μm, were deposited on silicon or sapphire substrates and provided with contact electrodes, which formed a Schottky contact with the GaN layer. It was, however, found that a reliable detection was limited to X-ray radiation with an energy value below 20 keV. For practical applications of a radiation detector, for example in dosimetry, a sensitivity to X-ray radiation with an energy value above 20 keV is, however, required.
Finally, M. Hofstetter et al. describe in “Applied Physics Letters” Vol. 96, 2010, pp. 092110, a radiation detector for X-ray radiation, which contains a so-called HEMT (“high electron mobility transistor”) with a GaN-based multi-layer system. This radiation detector can likewise have disadvantages due to its multi-layer structure.
In practice, it has shown that the hitherto described GaN-based radiation detectors are not suitable, in particular due to their complex structure, a complex calibration and/or an insufficient sensitivity for routine application in dosimetry. Furthermore, no practical applications of GaN-based radiation detectors, for example in medical engineering, the material testing or radiation monitoring were hitherto described.
The objective of the invention is to provide an improved radiation detector by means of which the disadvantages of conventional radiation detectors are overcome. The radiation detector should be characterized in particular by a simplified structure, simplified operation and/or an increased sensitivity compared with conventional detectors. The objective of the invention is furthermore to provide measuring devices and applications of the radiation detector by means of which disadvantages of conventional techniques for detection of X-ray radiation are overcome.
These objectives are achieved by a radiation detector of the invention and by a measuring device of the invention, which contains at least one such radiation detector.